Soap stock used in the formulation of soap bars is generally comprised of both substantially insoluble, generally longer-chain soaps (e.g., C16 or C18 palmitic or stearic acid soaps) and more soluble, generally shorter-chain soaps (e.g., C12 lauric acid soaps).
The introduction of insolubilizing salts (e.g., the insolubilizing multivalent ion salts of the invention) to precipitate out both the soluble and insoluble soaps found in soap stock according to the common ion effect is not something the person of ordinary skill in the art would consider. In particular, for example, the reduction of soluble soap would be thought to reduce lathering and so there would be no incentive, in fact there would be disincentive, to add such insolubilizing salts.
Unexpectedly, however, applicants have found that the introduction of such multivalent ion salts actually causes the formation of multivalent ion soap complexes (formed from the reaction of multivalent ion and the soluble soap) and produce bars which both lather well and are also unexpectedly milder. Further, the complexes surprisingly enhance deposition of benefit agents, particularly benefit agents (e.g., perfume or other benefit agents solubilized in the soluble soap micelles) which, when in the presence of a greater quantity of soluble soaps, would more readily wash away.
U.S. Pat. No. 5,607,909 to Kafauver et al. discloses personal cleansing freezer bars containing 5-35% magnesium soaps. The multivalent ions claimed for use in the subject application specifically excludes magnesium.
U.S. Patent Publication No. WO 98/06810 to Hauwermeiren et al., discloses laundry detergent compositions having filler salts selected from alkali and alkaline earth metal sulfates and chlorides (sodium sulfate is a preferred filler). PCT Publication WO 98/38269 to Ramanan et al., discloses a laundry detergent bar with improved physical properties resulting from the formation of a complex of calcium and siliceous material in situ. WO 98/53040 to Ramanan discloses laundry bar with improved sudsing and physical properties having a metal anionic sulfonate surfactant complex.
All the above are laundry compositions and are not personal wash bar compositions comprising 40% to 80% soap wherein soap exceeds level of synthetic, if any, by at least 10% by wt. Further, as laundry bars, the compositions comprise builders (e.g., phosphate or other builders) and/or enzymes. Compositions of the subject invention comprise less than 2%, preferably less than 1% by wt. builder, if any, and preferably are substantially free of builders. Further the compositions of the subject invention are substantially free of enzymes, since such enzymes would not be used in personal wash compositions.
U.S. Pat. No. 6,660,699 to Finucane et al., discloses the use of inorganic salts, e.g., calcium chloride, as latent acidifiers in bars comprising both soaps and synthetic surfactants. These latent acidifier salts remain as salts in the bar even after bar processing and do not react with fatty acid soaps or other alkaline material in the bar to form free fatty acid during bar formation. It is only as the bar is used/diluted in water that the latent acidifiers neutralize harsh soap or other alkaline materials in the bar, or reduce pH of bar through other acid-base interaction, to create mild cleansing action.
By contrast, the salts added in the composition of the invention do in fact predominantly react during bar processing (i.e., with soluble short-chain complexes) to precipitate insoluble soap complexes in the final bar. The increase in solid content (from the formation of insoluble soap complexes) allows the use of higher levels of other ingredients like mild syndets, oils or short chain fatty acids (i.e., normally too much of these components make bars too mushy and/or not hard enough for good processing). Thus, the insoluble complexes allow more of such above named ingredients to be used without compromising hardness while at the same time introducing the benefit associated with these ingredients, i.e., enhanced lather. Moreover, the reduction in solubility (again due to the insoluble complexes) enhances deposition by preventing benefit agents which would normally be washed away with the soluble soap from being so readily washed.